[660] See Prof. Owen’s observations on the bones that have been regarded as referable to the extremities of this creature, and especially on the phalangeal and other bones of the Mosasaur of the New Jersey greensand; Monog. Cret. Rept. 1851, pp. 36-40.
Prof. Goldfuss has described the remains of another and smaller species of Mosasaurus (M. Maximiliani), from Upper Missouri, U.S.; and Prof. Owen, in Dixon's "Fossils of Sussex," has established a third and still smaller species (M. gracilis),[661] to which he refers the four or five mosasaurian vertebræ found in the Chalk of Sussex. Two of these (caudal) are figured in Geol. S. E. p. 146, and Petrif. Lign. 44; and these and others are lithographed in plate viii. of Prof. Owen’s Monog. Cret. Reptilia, 1851.
[661] See also Monograph on the Reptiles of the Chalk, 1851, p. 31, and plate ix.
The remains of Mosasaurus occur also in the cretaceous sands of New Jersey, U. S. (See Dr. Morton’s Synopsis of the Organic Remains of the United States, 1834; and the Quart. Journ. of the Geological Society, vol. v. 1849.)
Leiodon anceps.[662]—Under this name Professor Owen has described a splendid fossil, consisting of a portion of the lower jaw of an acrodont reptile, with teeth, obtained by Edward Charlesworth, Esq. from the Chalk north of the Thames. This specimen was submitted to my inspection, many years since, by Mr. Charlesworth, and I then pointed out the analogy of this acrodont jaw to that of the Mosasaurus.
[662] Ibid. p. 42, pl. ix. A.
Prof. Owen in 1840 (Odontog. p. 261), and in 1841 (Rep. Brit. Assoc. p. 144), described and figured some teeth from the same specimen, which were lent by Mr. Charlesworth. These teeth the Hunterian Professor regarded as characteristic of a new genus of Mosasauroid reptile, to which he gave the name Leiodon (in allusion to the smoothness of the teeth). In 1845 (Rep. Brit. Assoc. p. 60) Mr. Charlesworth noticed, and in 1846 (London Geol. Journal, p. 23, plates iv. and vi.) figured and described, the above mentioned portion of jaw with teeth, under the name Mosasaurus stenodon; and in 1851 Prof. Owen figured and described this specimen under the name of Leiodon anceps, which was originally proposed for the animal, as known from its teeth, in 1840.
The portion of bone on which the teeth, five in number are implanted is seven inches in length, and is, in Professor Owen s opinion, the dentary piece of the lower jaw, and not a portion of a pterygoid bone. Mr. Charlesworth has had a section made of four of the teeth, and finds that the pulp-cavities are more or less occupied with solid cones of silex, which must have permeated the osseous parietes of the teeth.